This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Trace metal ions play a critical role in biology. One critical aspect of understanding the inorganic physiology of trace metals is detection of the distribution of the elements in tissues. In this proposal we will be utilising XRF imaging to study the metal homeostasis. Zebrafish embryos with increasing levels of copper deficiency have been designed using genetic mutation and copper chelators. As copper levels decrease, non-essential copper dependent processes, such as pigmentation, are lost. Then notochord development is affected and finally neurological deformation. A copper hierarchy has been identified where copper is target to more essential systems first and then to non-essential systems. It is unknown whether this hierarchy is enforced on a systemic level or a cellular level, is copper targeted to the cells responsible for neurological development over those responsible for pigmentation, or is copper delivery equal in all cells but the threshold cellular copper levels need to express the proteins responsible for pigmentation higher that those needed for expression of more essential proteins. XRF imaging will be used to study the distribution of copper in Zebrafish embryos to map the system wide trafficking of this metal.